Method of fabricating and installing the grip of a hand-held implement

ABSTRACT

A grip for the handle of a hand-held implement that, in as-produced form, is comprised of a thin walled tubular member open at one end and a boot integral with the tubular member that closes its other end. The grip&#39;s average internal girth along its longitudinal axis, as produced, is substantially less than the average external girth of the implement&#39;s handle portion to be covered by the grip along that handle portion&#39;s longitudinal axis. The grip, which may have a novel exterior gripping surface, is produced by dipping a male mandrel into an elastomeric latex and, thereafter, curing the latex skin formed on the mandrel prior to stripping of the grip from the mandrel. The grip is installed on an implement&#39;s handle by creating a pressure differential between the interior and exterior of the grip, thereby causing the grip to stretch radially outward from its longitudinal axis. This stretching step allows the implement&#39;s handle to be inserted through the grip&#39;s open end until the handle&#39;s free end bottoms out in the grip&#39;s boot. Subsequently, the pressure differential is released, thereby causing the grip to stretch into a tight friction fit with the handle. The grip&#39;s boot may thereafter be removed by slicing off, if desired.

This invention is directed to hand-held implements. More particularly,this invention is directed to a unique grip for hand-held implements,and to unique methods of fabricating and installing same.

There are, of course, numerous different hand-held implements in usethroughout the country today. Hand-held implements, basically, fall intotwo classes. The first class includes those hand-held implements usedfor work, and the second class includes those used for pleasure. In thefirst class are small hand tools such as screw drivers, hammers,chisels, wrenches, pliers, and the like, and large hand tools such asrakes, hoes, pruning shears, shovels, wheelbarrow handles, and the like.The second class mainly includes sporting goods equipment such as golfclubs, baseball bats, tennis rackets, paddle tennis paddles, badmintonrackets, hockey sticks, canoe paddles and the like. The common basiccharacteristics to each of these hand-held implements, from thestandpoint of this invention, are certain common characteristics of eachimplement's handle.

A first hand-held implement characteristic of importance to the grip ofthis invention, and the installation method associated therewith, isthat the implement's handle must be generally linear (although notnecessarily absolutely straight, as a slightly curved handle may beused) in configuration from one end to the other. That is, one end ofthe handle must be connected to the working head of the implement butthe other end must not be connected to that implement's working head.Such a handle is hereinafter referred to as a free-end handle. Each ofthe implement examples noted in the above paragraph, in the most commonform of each, possesses a free-end handle. An example of a handle on ahand-held implement which is connected at both ends to the implement'sworking head is a hand-held carpenter's saw of the cross-cut or riptype, i.e., the handle for a regular hand-held carpenter's saw is in theform of a closed loop connected to the saw's blade. The grip of thisinvention is not adapted for use on such a carpenter's saw.

A second hand-held implement characteristic of importance to the grip ofthis invention, and installation method associated therewith, is thatthe free-end handle's external girth and cross-sectional area may wellvary from one end to the other depending on the hand-held implementunder review, and that handle also may be symmetrical or asymmetricalalong its longitudinal axis from one end to the other. Indeed, the gripof this invention, and the method of installation associated with it,are well suited to accommodate such a variance in one or more ofexternal girth, cross-sectional configuration, and symmetry, from oneend to the other of an implement's free-end handle. For example, thehandle of a hammer is generally linear (but may not be exactly linear)from one end to the other, and is connected to the hammer's head at oneend but is free or unconnected at the other end, but the external girthand cross-sectional configuration of that handle varies from one end tothe other, and the handle may well be non-symmetrical about itslongitudinal axis from one end to the other; such variations occur, ofcourse, because hammer handles are often shaped in an effort toaccommodate a user's hand to achieve the easiest possible work positionfor that user's hand. The grip and installation method of this inventionare well suited for use with such a hammer handle. Another example, andthe example by which the grip of this invention will be described indetail below, is a baseball bat's handle. A bat's handle is exactlylinear, and is symmetrical about its longitudinal axis, from one endthereof to the other, but the bat's handle varies widely in its externalgirth and cross-sectional area from one end to the other along itslongitudinal axis. As is well known, a baseball bat's handle necks downfrom a relatively large diameter for that portion adjacent the bat'shead to a relatively small diameter for that portion adjacent the bat'sknob, the knob itself terminating the handle end of the bat. Thebaseball bat handle has been chosen to illustrate the grip of thisinvention, and the installation method associated therewith, for thereason that same illustrates a handle having widely differing externalgirths from one end to the other, thereby illustrating the wide latitudeand adaptability of the grip of this invention and installation methodassociated therewith.

Accordingly, it has been a primary objective of this invention toprovide a novel grip for the handle of a hand-held implement, thestructural concepts of the grip being adaptable for use in a widevariety of hand-held implements each having, as the basic structuralcharacteristic connecting those implements, a generally linear (althoughnot necessarily absolutely straight) handle connected at only one end tothe tool's working head.

It has been another objective of this invention to provide such a novelgrip that includes unique exposed gripping surface characteristics, samepermitting the user to obtain and maintain good purchase on animplement's handle on which the grip has been installed.

It has been still another objective of this invention to provide a novelmethod of producing the novel grip for the handle of a hand-heldimplement, that novel method permitting the grip to be provided withstructural characteristics that allows the simple and easy installationof same on a generally linear handle regardless of the external girthand cross-sectional area variation in that handle from one end thereofto the other, and regardless of the symmetry or lack thereof from oneend thereof to the other.

It has been a further objective of this invention to provide a novelinstallation method for the novel grip on a free-end handle of ahand-held implement, the installation method permitting an originalequipment grip to be easily, simply, and quickly installed during theinitial manufacture of the hand-held implement in a factory environment,and also permitting a replacement grip to be easily, quickly and simplyinstalled in a use or in-the-field environment.

These objectives and advantages are provided in the grip for the handleof a hand-held implement of this invention, which grip is comprised, inthe as-manufactured attitude, of a generally linear and generallytubular member open at one end and closed at the other end by a bootintegral with the tubular member. The grip's average internal girth fromone end to the other, as produced, and before installation on a handle,is substantially less than the average external girth of the implement'shandle from one end to the other as to that handle position where thegrip is to be mounted. The grip is fabricated of an elastomeric latex,e.g., a rubber latex, having a relatively high percentage elongation atbreak, a relatively high tensile strength at break, and a relatively lowmodulus. The grip is produced by dipping a male mandrel having thegrip's approximately as-produced (and before-installation) size andgeometry, and as-produced gripping surface, into the elastomeric latex(the mandrel preferably being preheated prior to dipping), andthereafter curing the latex skin formed on the mandrel (that curingpreferably being accelerated by exposure of the mandrel to an elevatedtemperature after dipping). After curing, the grip is stripped from themandrel and turned inside out, thereby orienting the grip's exteriorsurface on the outside face of the grip. This dipping fabrication methodpermits the grip to be provided with a relatively thin wall of a highlyelastomeric material that provides the tensile strength at break,percentage elongation at break, and modulus, desired. These desirablegrip characteristics, in turn, permit the grip to be installed verysimply, easily and quickly on a free-end handle of a hand-heldimplement, either at the initial production location of the implement orin the field, by creating a pressure differential between the interiorand exterior of the grip sufficient to expand the grip into an internalgirth throughout its length which is greater than that handle section(within that handle portion on which the grip is to be mounted) havingthe largest external girth. After expanding or stretching of the grip,the implement's handle is simply inserted into and through the grip'sopen end until the handle's free end bottoms out in the grip's boot. Thepressure differential is thereafter released, thereby permitting thegrip to contract back toward its as-produced geometry and dimensionsinto a tight friction fit with the handle since the average internalgirth of the grip as manufactured is substantially less than the averageexternal girth of the handle within that handle portion where the griphas been mounted.

Other objectives and advantages of this invention will be more apparentfrom the following detailed description taken in conjunction with thedrawings in which:

FIG. 1 illustrates a novel grip for a baseball bat handle asmanufactured in accord with the principles of this invention;

FIG. 2 illustrates a detailed section of the grip's tubular member asshown in FIG. 1, the tubular member's section having been slit along aline parallel to the grip's longitudinal axis and laid flat, that detailillustrating the novel cushion or pad configuration provided on thegrip's exterior or gripping surface;

FIG. 2a is a cross-sectional view taken along line 2a--2a of FIG. 2;

FIG. 3 illustrates a first method, in accord with the principles of thisinvention, of fabricating the FIGS. 1 and 2 grip;

FIG. 4 is a view similar to FIG. 3 illustrating a second method offabricating the FIGS. 1 and 2 grip;

FIG. 5 illustrates a first step in installing the FIGS. 1 and 2 grip ona baseball bat's handle, and the apparatus used in connection therewith;

FIG. 6 is a view similar to FIG. 5 illustrating a second step ininstalling the FIGS. 1 and 2 grip on the baseball bat handle;

FIG. 7 is a view similar to FIGS. 5 and 6 showing insertion of thebaseball bat handle into desired positional relation with the FIGS. 1and 2 grip after a pressure differential has been established betweenthe interior and exterior of the grip;

FIG. 8 is a view similar to FIG. 7 showing the FIGS. 1 and 2 grip in atight, friction-fit relation with the baseball bat handle after thepressure differential has been released; and

FIG. 9 shows the baseball bat with the FIGS. 1 and 2 in final frictionfit or fixed position thereon and removed from the installationapparatus.

As previously mentioned, the grip for the handle of a hand-heldimplement of this invention, and the methods of producing and installingsame, for purposes of illustration of this invention, will be describedin connection with a grip 10 for a baseball bat 11. The bat's elongatedor longitudinally extended free-end handle 12 is linear in configurationfrom one end 12a to the other 12b with end 12a being connected to thebat's working head 11a but end 12b being disconnected from the workinghead 11a. Further, and in this bat 11 environment, the inner 12a andouter 12b ends of the bat's free-end handle 12 are displaced one fromthe other a distance equal to the handle's length 12c, and the handle'sfree end 12b is also displaced from the bat's working head 11a at adistance equal to the handle's length. This general physical relation ofthe handle's ends 12a, 12b one with the other, and with the bat'sworking head 11a, is the same as is found in many other hand-heldimplements, among which are those recited in the second paragraph ofthis description. Note further that the bat's handle 12 is rigid, i.e.,does not bend along its length from one end to the other; thischaracteristic is also common to the previously recited hand-heldimplements in the second paragraph of this description. The grip 10itself is illustrated in FIG. 1, that Figure illustrating the gripas-produced and prior to installation on the baseball bat's handle 12.As is readily apparent from FIG. 1, the grip 10 is linear from open end10a to closed end 10b, and is symmetrical about the centerline 13. Thegrip 10, as manufactured, is formed of two basic portions. The firstportion is a cylindrical and tubular grip portion 14 that is open toatmosphere at open end 10a. The second portion is a boot 15 portionformed integral with the tubular portion 14 at that end of the gripopposite to the open end 10a, thereby providing the closed end 10b(i.e., closed to atmosphere) of the grip. The boot 15 itself is shapedin the general configuration of knob 16 at the free end 12b of thebaseball bat's handle 12.

The average internal girth IG of the grip's tubular portion 14 (from oneend 14a to the other 14b along its axis 13) is preferably at least about5% less than, and no more than about 50% less than, the average externalgirth EG of the bat's handle portion 12 to be covered by the grip 10(i.e., the handle's gripping portion) from one end 12a to the other 12balong its axis 11b. Indeed, the internal girth IG of the grip's tubularportion 14 may well fall within this percentage dimensional relationvis-a-vis the external girth EG of the handle's grip portion 12 at allpoints along its axis 13 in certain end use applications. However, theimportant criteria is that the internal girth IG of the grip's tubularportion be sized and configured relative to the external girth EG of thehandle's grip portion 12 from one end 12a to the other 12b so as toprovide a relatively tight friction fit after the grip 10 has beeninstalled on the handle 12. Girth, as used in connection with thisinvention, refers to the inside peripheral dimension of the grip 10 andto the outside peripheral dimension of the implement's handle 12 asmeasured in a plane transverse to the respective axes 13, 11b of thegrip and handle.

As an example, the grip's inside diameter 14c within tubular portion 14may be about 0.90 inches for a major league baseball bat. A typical suchbat has an average external diameter 12d of about 1.15 inches from oneend 12a of the handle to the other 12b (excluding the knob 16 portion ofthe handle). This provides an average internal girth IG for the tubularportion 14 that is about 22% less than the average external girth EG ofthe bat's handle 12 for the presently preferred embodiment. That portionof the bat's handle 12 used in computing the average external girth EGis that portion which will be covered by the cylindrical portion 14 ofthe grip 10 shown in FIG. 1. This dimensional relationship of the grip'sinternal girth IG to the baseball bat handle's average external girth EGrequires that the grip's tubular portion 14 must be substantiallystretched outwardly (away from centerline 13) in a radial fashionthroughout its length 14e in order to install same onto the baseballbat's handle 12, and permits the grip, once it is installed on thebaseball bat's handle, to be frictionally held in fixed relation theretoas long as the material from which the grip is fabricated is arelatively high friction material such as rubber which tends not to slipagainst the substrate on which it is carried. Although the dimensionalrelationship of the grip's tubular portion 14 to the baseball bat'shandle portion 12 is most important because the tubular portion 14includes the grip's handgrip section 17 adapted to be gripped by auser's hand, it is also worth noting that the inside major dimension 15aand inside minor dimension 15b of the grip's boot 15 is substantiallyless than the similar external dimensions of the bat's knob 16. Hence,the boot 15 must also be stretched substantially to permit the bat'sknob to be placed in operational relation therewith. It will beunderstood, therefore, that the grip's internal girth IG may vary fromone end 10a to the other 10b, and may vary in cross-sectional geometry(as opposed to the cylindrical cross-sectional configuration of thegrip's tubular portion 14) if such were necessary to accommodate ahand-held implement's handle which had a widely varying external girthEG and/or cross-sectional geometry from one end thereof to the other.

The average wall thickness 10c throughout the overall length 10d of thegrip 10 must be thin enough to permit stretching of the grip (asdescribed in detail below) upon exposure to relatively low pressuredifferentials, e.g., perhaps even as low as 2 psi under certainconditions, between the grip's inner and outer surfaces. A typicalaverage wall thickness 10c for the bat handle's grip 10 throughout itslength 10d, which thickness will also depend to some extent on theelastomeric material from which the grip is fabricated, may be about0.04 inches (the grip's wall thickness being shown greatly enlarged forillustrative purposes in FIG. 1). A grip 10 fabricated in accord withone of the formulations set out below, and with the wall thicknessdimension and configuration heretofore mentioned, will stretch uponexposure of a pressure differential of about 6-7 psi (and, particularly,upon exposure to a vacuum about 12-20 inches mercury). This wallthickness 10d may be thicker in the grip's boot portion 15 thanthroughout the grip's tubular portion 14 since that area will be exposedto greater wear from scuffing on the ground during use on a baseballdiamond if that boot is not removed after installation of the grip 10onto the baseball bat 11. It is preferred, therefore, that the averagewall thickness 10c of the grip 10 be between about 0.01 inch and 0.10inch; this wall thickness range is preferred because beneath the lowerlimit the grip would not have sufficient durability to provide a usefullife to the user, and above the upper limit of the range it is believedthe grip could not be installed with relatively low pressuredifferentials by the installation method of this invention.

It is preferred that a portion 17 of the external surface area of thegrip's tubular portion 14, namely, that portion where the grip 10 isadapted to be held by the user's hands, be provided with a series ofcushions 18 in a particular geometric configuration thereon. Asillustrated in FIG. 2, portion 17 of the cylindrical portion 14 of thegrip 10, throughout and around the exterior periphery of that portion17, is provided with a series of cushions or pads 18 raised or elevatedout of the exterior base surface 19 of the grip to a height 18a. Thepads 18 are generally elliptical in shape, and are sub-grouped into aseries of longitudinal strips extending in spaced parallel relation fromadjacent one end 14a to adjacent the other end 14b of the grip's tubularportion 14 about the outer periphery of that tubular portion 14. Thelongitudinal pad 18 strips are indicated by centerlines 21. The multiplelongitudinal strips 21 of pads 18 are separated one from the other bylongitudinal (but not necessarily linear) sweat main-channels (indicatedby centerlines 22) which are, of course, in the nature of valleysdefined by the upraised pads. Furthermore, the pads 18 within eachlongitudinal strip 21 are likewise separated one from the other by sweatsub-channels (indicated by centerlines 23a, 23b, 23c), these sweatsub-channels being angulated relative to the central longitudinal axis13 of the grip 10 (and, hence, relative to the longitudinal stripchannels 22). These sub-channels 23 are also in the nature of valleysdefined by the upraised pads. Note that the sweat sub-channels 23 (eachof which is generally saw-toothed in configuration) within each stripchannel 22 are disposed parallel one to the other about the grip'soutside circumference throughout portion 17 of the grip's tubularportion 14. It is preferred that the saw-tooth sub-channels 23 each beangled at about 45° relative to the longitudinal channels 22. Of course,and while the sweat sub-channels 23 are shown in saw-tooth fashion onthe outer surface of and about the circumference of the grip 10, samealso may be disposed in simple parallel circular fashion about the outerperiphery. Thus, the grip's exterior surface area, within pad portion 17of the handle's tubular portion 14, is provided with longitudinal sweatmain-channels 22 and with circumferential sweat sub-channels 23, samecooperating to function in permitting the sweat from the user's handswhich grip the grip's pad portion 17 to be drained away from beneaththose hands, all in an effort to maintain a not-slip relationship, i.e.,to maintain good purchase, between the user's hands and the grip of thisinvention regardless of the hand-held implement on which it is used. Inaddition to the enhanced frictional contact or purchase of the user'shands with the grip 10 because of the pads 18; and the sweat channels22, 23 provided, the upraised pads also provide a cushioning effect tothe user's hands. For example, and where the grip 10 with pads 18 isused on a baseball bat 11, the batter feels less sting in his hands whenhe mis-hits a ball with the bat. Such is, of course, especially usefulin connection with bats used in municipal baseball leagues for children.It is preferred that the pads 18 be upraised at least about 0.005 inchesoff the outside surface 19 of the grip to provide the cushionadvantages, as well as the perspiration drainage advantages, which thegrip 10 structure of this invention provides to the user. While the pads18 are shown as elliptical for purposes of illustration, same may berectangular or trapezoidal or even of a generally random geometry, theimportant point being a multiplicity of upraised pads 18 which definesweat channels 22 and/or 23 at least one of longitudinally andcircumferentially of the grip. Additionally, the pads 18 themselves maybe textured or roughened on their exterior or top surface 24 to provideincreased frictional contact between the user's hands and the grip'stubular portion 14. Roughened or textured pads 18, in combination withsmooth channels 22, 23 provided to enhance escape of prespiration frombetween the user's hands and the grip, proves quite effective andprovides a very practical grip 10 highly useful in the field regardlessof the implement on which the grip of this invention is used.

The material from which the grip 10 of this invention is fabricated maybe any material which is sufficiently impermeable to air to withstand apressure differential, and which will provide the desired tensilestrength at break, percentage elongation at break, and modulus at 200%elongation characteristics (all as measured by ASTM Test Number D412-68). The tensile strength at break of the material is preferablyabout 2000 psi to about 6000 psi, the percentage elongation at break ispreferably about 400 to about 1000%, and the modulus at 200% elongationis preferably about 100 psi to about 500 psi. Also, the materialpreferably should have a tension set at 600% elongation no greater thanabout 2 to about 20% (also as measured by ASTM Test Number D 412-68).The material used also preferably provides the interior surface 25 ofthe grip 10 with a relatively high static coefficient of friction, e.g.,between about 0.8 and about 1.2 (as computed in accord with testinformation set out on Pages 217-219 of Mechanical Engineer's Handbook,edited by Lionel S. Marks, Fifth Edition, McGraw-Hill Book Co., Inc.,New York, N.Y. 1951), since it is desirable that the grip be held in anon-slip frictional engagement with the handle 12 of the bat 11 (orother hand-held implement, and whether that handle be fabricated ofwood, metal or plastic) so as to prevent any substantial slippage of thegrip over the handle upon use of the bat, all as described in detailbelow. Under certain circumstances it may be desirable to coat a glue ofsome type on the bat's handle 12 prior to installation of the grip 10thereon to enhance the fixed interconnection of the grip with thehandle, but the grip of this invention and the installation method ofthis invention for the grip permits installation to be accomplishedreadily and easily whether a glue is used or not as will be apparentupon further detailed description below. Of course, the exterior staticsurface friction of the grip 10 is primarily dependent on the materialfrom which the grip is fabricated, the surface design, i.e., the pad 18design, and pad surface 24 texture. Such may vary depending on the enduse of the implement itself (in some cases a greater static coefficientof friction may be desired on the exterior surface than on others).Additional desirable characteristics of the material from which the gripis made are that same should be relatively tear resistant, and should beable to withstand the elements, e.g., sun, rain, cold, as most hand-heldimplements with which the grip 10 of this invention are suited will beused outdoors at some point during the useful life of each. From aprocess standpoint in the manufacture of the grip of this invention, itis desirable that same be made from an elastomeric latex, for example, arubber latex such as a natural rubber latex, styrene butadiene rubberlatex, neoprene latex, or nitrile rubber latex.

The grip 10 for a hand-held implement 11 of this invention is preferablyproduced by dipping same in an elastomeric latex. Dipping is used, asopposed to molding or casting, because of the advantages provided in thegrip 10 itself which are described elsewhere in this invention.Particularly, dipping permits the elastomeric grip 10 to be providedwith a thin wall thickness 14d vis-a-vis a relatively extended length10d for the grip, thereby permitting the grip to be provided withdesired physical characteristics described above. The dipping methodused to produce the grip 10 of this invention may either be aheat-sensitive latex dipping method (see FIG. 3) or a coagulant latexdipping method (see FIG. 4), both methods making use of an elastomericlatex as the basic elastic material from which the grip is fabricated. Atypical heat-sensitive natural rubber latex compound which may be usedis as follows:

    __________________________________________________________________________      Compound Formula      Dry Parts by Weight                                   __________________________________________________________________________    Natural rubber from latex                                                                             100.0                                                 Nonyl phenoxy poly (ethylene oxy) ethanol                                                             0.3                                                   Sulfur                  2.0                                                   Zinc diethyl dithiocarbamate                                                                          1.0                                                   Sym di-beta-napthyl-p-phenylene diamine                                                               1.0                                                   Zinc oxide              0.5                                                   Poly vinyl methyl ether 0.75                                                  Carbon black            0.5                                                   Formaldehyde to pH 7.5 - 8.0                                                  Microcrystalline & paraffin wax blended                                        as anti-ozonant (Sunproof Regular from                                        Uniroyal Chemicals, Division of Uniroyal,                                     Inc., Naugatuck, Connecticut 06770)                                                                  3.0                                                   __________________________________________________________________________

A typical coagulant-sensitive natural rubber latex compound that may beused is as follows:

    __________________________________________________________________________      Compound Formula      Dry Parts by Weight                                   __________________________________________________________________________    Natural rubber from latex                                                                             100.0                                                 Nonyl phenoxy poly (ethylene oxy) ethanol                                                             0.3                                                   Sulfur                  2.0                                                   Zinc diethyl dithiocarbamate                                                                          1.0                                                   Sym di-beta-napthyl-p-phenylene diamine                                                               1.0                                                   Zinc oxide              0.5                                                   Carbon black            0.5                                                   Formaldehyde to pH 9.5 - 10.0                                                 Microcrystalline & paraffin wax blended                                        as anti-ozonant (Sunproof Regular from                                        Uniroyal Chemicals, Division of Uniroyal,                                     Inc., Naugatuck, Connecticut 06770)                                                                  3.0                                                   __________________________________________________________________________

The heat-sensitive latex dipping method is illustrated in FIG. 3. Asshown in that FIG. 3, a series of male mandrels 31 are fixed in positionon an endless conveyor chain 32, each mandrel having the approximatedimensions and exact configuration (e.g., for pads 18, sweat channels22, 23, inside diameter 14c, boot dimensions 15a, 15b) on its exteriorsurface as is desired for the bat grip 10 illustrated in FIGS. 1 and 2.In practice, the actual dimensions of the mandrel will be about six toseven percent (6-7%) oversized relative to the desired dimensions of theas-produced grip 10 to allow for a limited degree of shrinkage in thegrip's dimensions during curing if a composition in accord with one ofthe above formulations is used. The endless chain 32 is adapted to movein the direction of arrows 33 between opposed end sprockets 34a, 34b,each mandrel 31 on the lower run 32a of the chain passing through apreheat oven 35 having a temperature between about 140° and about 180°F. for between about 15 minutes and about 30 minutes, and each mandrel31 on the upper run 32b of the chain passing through a curing oven 36having a temperature between about 170° and about 190° F. for betweenabout 120 minutes and about 180 minutes. A drive mechanism (not shown)is connected with one of the sprockets 35 for moving the mandrels in thedirection of arrows 33. At one end of the chain's run, and adjacentsprocket 34a, there is provided a tank 37 adapted to receive a charge ofthe heat-sensitive latex of the compounding set forth above. The latexdip tank 37 is mounted on platform 38 which is vertically movablebetween a storage position (shown in solid lines) and a dipping position(shown in phantom lines) by a hydraulic motor 39 fixed to ground. Aftereach mandrel 31 has passed through the preheat oven 35, and as eachmandrel is disposed over the latex dip tank 37, the hydraulic motor 39raises the dip tank from the solid line to the phantom line position soas to coat the mandrel with a skin-like coating 40 of the natural rubberlatex compound. The dip tank 37 is then lowered back into the solid lineposition by the motor 39 so that the mandrel can proceed past thedipping station into the curing oven 36. Each mandrel 31 is soprocessed, and as succeeding mandrels are dipped preceding mandrels passthrough the cure oven 36 to the strip station 41 adjacent sprocket 34bat the other end of the endless chain 32. Each dipped grip 10 is thenstripped from its mandrel 31 simply by pulling same off at the stripstation in an inverted fashion, then washed, dried, and thereafter thetop edge 14a of the grip is trimmed if necessary to provide a standardlength 10d product. The exterior surface texture of the grip's pads 18,channels 22, 23 and boot 15 is, as previously noted, provided by theexterior surface of the machined mandrels 31.

A coagulant latex dipping method is illustrated in FIG. 4, the referencenumerals used in describing the FIG. 3 method also being used toidentify like equipment in FIG. 4 method. The primary difference betweenthe coagulant latex dipping method and the heat-sensitive latex dippingmethod, from an equipment standpoint, is the provision of a coagulantdip tank 43 in addition to the latex dip tank 37. As shown in FIG. 4,the coagulant dip tank 43 is provided upstream of the latex dip tank 37vis-a-vis the travel direction 33 of the endless chain conveyor 32. Thecoagulant dip tank 43 is mounted on a platform 44 which is verticallymovable by means of a hydraulic motor 45 fixed to ground, the coagulantdip tank being moved between a storage position (shown in solid lines inFIG. 4), and a mandrel dipping position (shown in phantom lines in FIG.4). The coagulant dip tank 43 and latex dip tank 37 dipping oroperational sequence is controlled by timing means (not shown) that isresponsive to the relative position of the mandrels vis-a-vis thosetanks. The coagulant latex dipping method also makes use of the samemandrels 31 used in the heat-sensitive method, the difference being thateach mandrel is first dipped in a coagulant prior to dipping in theelastomeric latex. The coagulant in the coagulant dip tank 43, for thatcoagulant-sensitive natural rubber latex compound recited above, may bea solution of calcium nitrate in ethanol at a specific gravity of about1.2. In the coagulant-sensitive dipping method, the preheat oven 35 isat a temperature between about 120° and about 140° F. and the cure oven36 is at a temperature between about 170° and about 190° F., eachmandrel's dwell time within the preheat oven being between about 15minutes and about 30 minutes and each mandrel's dwell time within thecure oven being between about 120 minutes and about 180 minutes.

As previously noted, either the heat-sensitive latex or the coagulantlatex dipping method is used to fabricate the grip 10 of this inventionin order to provide a grip having the desired physical characteristicsin accord with the principles of this invention. While either dippingmethod may be used, the heat-sensitive dipping method is preferred atthis time for practical reasons because only one dip of each mandrel 31is required, i.e., because the mandrel needs only be dipped into thelatex tank 37 and does not require a preliminary dipping into acoagulant tank 43.

A grip for an elongated or longitudinally extended handle of a hand-heldimplement (e.g., a baseball bat's handle), fabricated in accord with theprinciples and characteristics as set forth for this invention, may beeasily and simply installed onto the implement's handle where the handleis rigid (i.e., non-bending) along its length and where the handle'sfree or outer end is displaced from the handle's inner end (which innerend of the handle is attached to the handle's working head) a distanceabout equal to the handle's length. A unique feature of the novel grip10, and of the novel grip installation method, is that the grip may beinstalled in the field (e.g., in the case of a replacement grip) aseasily as in the place of initial manufacture. This for the reason thatthe installation method requires, for its implementation, only a vacuumsource 51 and a simply constructed vacuum chamber 52.

As shown in FIG. 5, the vacuum chamber 52 includes an outer tube 53closed at bottom end 53a by floor 54 and at top end 53b by ceiling 55.The outer tube 53 includes a vacuum port 50 having a fitting 56. Aninner tube 57 is disposed within the closed outer tube coaxially withouter tube 53 on axis 58. The inner tube 57 is elevated at its bottomend 57a above the floor 54 of the outer tube 53, and is of an overalllength that permits same to extend out of the outer tube's ceiling 55 atits top end 57b into the atmosphere. The inner tube 57 has a slottedside wall, the slots 59 running parallel to the axis 58 of the vacuumchamber structure 52 but the slots 59 being provided in the side wallonly interiorly of the outer tube 53. In other words, that portion 60 ofthe inner tube 57 (which, in a sense, forms a collar for the vacuumchamber 52) which extends up and out of the outer tube 53 has no slotstherein, the joint 61 between the inner tube's collar 60 and the outertube's ceiling 55 being airtight. Floor 62 of the inner tube 57 is alsoprovided with holes 63 therein. Thus, that portion of the inner tube'swall and floor which are interior of the outer tube is air permeable,i.e., not airtight.

As shown in FIG. 5, a vacuum pump 51 (of a capacity sufficient to draw avacuum of at least about 12-20 inches mercury) is interconnected withthe outer tube's fitting 56 by flexible hose 64. The vacuum pump 51 maybe of any hand operated, foot operated, or motor driven vacuum pumpstructure that is commonly known to those skilled in the art. A usefulhandgun type vacuum pump 51 is that marketed under the trademark MITYVACby Neward Enterprises, Inc., Upland, Calif. 91786. Another manuallyoperated vacuum pump is disclosed in U.S. Pat. No. 963,528. Generallyspeaking, the handgun type vacuum pump 51 (or foot operated vacuum pump,not shown) is highly useful in the sense that same may be used in thefield, under certain conditions, to replace worn out grips 10 on thehandles 12 of baseball bats 11. In other words, the hand vacuum pump 51and vacuum chamber 52 structure illustrated in FIG. 5 may be used by abaseball coach at the baseball playing field to replace worn out gripswith new replacement grips onto used baseball bats under certainconditions. It is understood, however, that more elaborate vacuumchamber 52 structures which are mechanically operated may be devised andused in a manufacturing facility for baseball bats 11 where grips 10 areinitially provided on the bats as original equipment.

Note that the length 57c of the inner tube 57 in the vacuum chamber 52structure (see FIG. 5) is slightly less than the length 10d of thebaseball bat handle's grip 10 as initially produced (see FIG. 1), andthat the internal diameter 57d of that inner tube 57 throughout itslength 57c is substantially greater than the maximum diameter 15a of thegrip's knob 15. Thus, and as an initial step in the installation of thegrip 10 on the baseball bat's handle 12, the grip is dropped into thevacuum tube structure's inner tube 57 until the grip's boot 15 rests orsits on the ported floor 62 of the inner tube. In other words, the innertube 57 (and, therefore, the vacuum chamber 52) is sized and configuredthroughout its length 57c to receive the grip 10 in inserted relationtherein until the grip's boot is seated on a floor within the vacuumchamber. This orientation of the grip within the vacuum chamber 52, ofcourse, exposes the open end 10a of the grip's tubular portion 14 toatmosphere, and orients the grip's open end adjacent the open end 57b ofvacuum tube 57, yet permits the top end section 66 of the grip's tubularportion to extend above the inner tube 57 (and, hence, extend outside ofthe vacuum chamber 52 structure). After initially locating the bat'sgrip 10 in the vacuum chamber 52 structure in an upright attitude asshown in FIG. 5, the top end section 66 of the grip 10 is stretchedoutwardly by hand in a radial fashion from the grip's axis 13, and thenturned downwardly over the vacuum tube structure's collar 60. In otherwords, the open end of the grip is cuffed outwardly and downwardly intoa sealing interengagement with the vacuum tube's collar 60, compare FIG.5 to FIG. 6. This cuffing of the grip's top end section 66 with thevacuum tube's collar 60 creates an airtight chamber 67 (comprised ofsub-chambers 67a and 67b) within the outer tube, i.e., closes the vacuumtube's interior to the atmosphere.

After the grip 10 has been cuffed onto the vacuum tube's collar 60, apressure differential is created between the interior 70 and exterior 71of the grip sufficient to expand the grip into an internal girththroughout its longitudinal length 10d which is substantially greaterthan that handle section (knob 16 in the case of a baseball bat 11)having the largest external girth EG. In this embodiment, the pressuredifferential is created by drawing a vacuum within the vacuum chamber 52by operation of the handgun type vacuum pump 51. A vacuum in the amountof about 12 inches Hg to about 20 inches Hg is all that need be pulledif the grip 10 has the physical characteristics before mentioned aspreferable. The vacuum is pulled simply by manually retracting thehandgun type pump's trigger 68 toward the pump's handle 69 a number oftimes until the entire grip 10, i.e., until the grip's tubular portion14 and the grip's knob portion 15, has been sucked or drawn outwardlyinto supporting contact with the interior surface of the slotted innertube 57. The slotted inner tube 57 functions to insure that the grip 10is expanded or stretched outwardly under the vacuum in a symmetricalfashion. If the slotted inner tube 57 were not provided, under certainoperational conditions it is possible that the grip 10 might be suckedagainst the vacuum tube's vacuum port 55, thereby closing the vacuumport prior to completely stretching the grip into the attitude which thegrip would assume upon full exposure to the vacuum (which vacuumattitude of the grip is shown in FIG. 7).

An alternative vacuum chamber structure (not shown) to that shown inFIGS. 5-8 eliminates the slotted inner tube 57 but retains collar 60,thereby providing only a single tube chamber. In this alternativestructure, a groove extending upwardly and longitudinally from thevacuum port on the surface of the tube's inside wall, and narrow enoughto prevent the grip from expanding into same, may be provided to insureadequate air exhaust upon drawing the vacuum, thereby preventingpremature closing of the vacuum port by the expanding grip. The samesymmetrical stretching effect upon drawing a vacuum in this alternativevacuum chamber structure also can be accomplished by providing a channelleading away from the vacuum port which is defined by two parallel ribsthat protrude inwardly from the single tube's inside face, the ribsbeing spaced close enough one to the other to prevent the grip fromexpanding into the channel defined by same and, thereby, preventingblockage of the vacuum port prematurely before the grip has beencompletely expanded throughout its length.

Once the pressure differential (which pressure differential between theinterior 70 and exterior 71 of the grip 10 need be sufficient only toenlarge or stretch the grip's inside girth IG throughout the grip'slength 10d so as to be sufficient to accept the implement's handle 12)has been created by vacuum between the interior 70 of the grip 10 andthe exterior 71 of the grip so as to expand or stretch that grip awayfrom its center longitudinal axis 13 into contact with the insidesurface of the vacuum structure's inner tube 57, i.e., once sufficientvacuum has been pulled from the interior chamber 67 of the vacuumchamber 52 structure so as to stretch the grip out of its as-producedattitude shown in FIG. 1, the baseball bat may then be inserted handle12 first into the vacuum chamber 52 structure through the open top enddefined by the collar 60. The bat's handle 12 is simply inserted intoand through the grip's stretched-open top section 66 until the handle'sfree or knob 16 end bottoms out in the grip's boot 15 and, thereby,rests on floor 62. This positively locates the baseball bat's handle 12in the desired longitudinal relation, and in a substantially coaxialrelation, within the vacuum chamber 52 and, therefore, with thevacuum-stretched grip 10. There is, as previously mentioned, a definitedimensional relation between the vacuum chamber's interior size andconfiguration throughout its length 57c, i.e., interior diameter 57d ofthe vacuum chamber's cylindrical inner tube 57, and the exterior sizeand configuration of the baseball bat's handle 12 throughout its length12c. This dimensional and configurational relationship, which generallyspeaking is the same from a concept standpoint for the handle of anyhand-held implement vis-a-vis the grip to be provided thereon, is simplythat the tube 57, at the most constricted point along its axis 58, mustbe larger than the implement's handle at its largest point along itsaxis 116. In other words, in this connection, the inside dimensions andconfiguration of inner tube 57, i.e., of the vacuum chamber 52, aresized so as to permit a degree of expansion sufficient to accept theimplement's handle into the interior of the grip as expanded in theaforementioned manner without touching the grip during insertion of thehandle. This for the reason, of course, that the implement's handle mustbe insertable to the floor 62 of the vacuum structure's inner tube 57 soas to properly position and support the implement's handle 12 in thecorrect spatial orientation relative to the grip already in thestretched configuration within the vacuum chamber 52 structure.

After the baseball bat's handle 12 has been dropped into a supportedposition within the vacuum-stretched grip 10 located in chamber 52structure as shown in FIG. 7, the vacuum (i.e., the pressuredifferential) from the vacuum chamber 52 structure is released, therebypermitting atmospheric air to re-enter the interior 67 of the vacuumchamber 52 through port 55. When the vacuum is released, and due to theelasticity of the grip 10, the grip immediately attempts to contractback into its original as-produced attitude as shown in FIG. 1. However,and since the average external girth EG of the bat's handle 12 along itshandle length 12c is greater than the average internal girth IG of thegrip in its as-produced state along its length 10d, the grip stretchesinto a relatively tight frictional contact with the bat's handle fromone end 10a thereof to the other 10b as shown in FIG. 8. The degree offriction fit depends to some extent on the elastomeric material used, aswell as on the relation of the handle's average external girth EG to thegrip's average internal girth IG (the smaller the grip's averageinternal girth IG, the tighter the friction fit). Note particularly, inFIG. 8, that the grip's boot 15 is stretched around the bat's knob 16end, the baseball bat having been properly positioned vis-a-vis the knobportion of the grip 10 when the bat is initially inserted into thatposition as shown in FIG. 7. The open end or cuffed portion 66 of thegrip 10 is then uncuffed from its stretched relation with the vacuumtube's collar 60. This uncuffing also unrolls the grip's cuff 66 portioninto a stretched or friction fit interengagement with the baseball bat'shandle 12 as well.

If desired, and prior to insertion of the baseball bat's handle into thevacuum-stretched grip 10 as shown in FIG. 7, the handle portion of thebat may be provided with a coating of glue or other adhesive substance.This intermediate glue step, while not required under all circumstances,may be desirable to insure that the grip is retained in tight, fixedrelation with the handle, and does not slip relative thereto, when infinal friction fit position on that baseball bat, or other hand-heldimplement. The use or not of a glue also depends to some extent on thesubstrate (wood, metal or plastic) from which the implement handle isfabricated. Note that this installation method permits a liberalquantity of glue to be so applied to the bat's handle with no worry thatthe grip will scrape it off, or otherwise reduce the effectivenessthereof, as the grip is installed for the reason that the grip simplycontracts radially (relative to the grip's axis 13) from its expandedattitude into direct contact with the implement handle's exteriorsurface after the implement's handle 12 has been positioned as shown inFIG. 7 and upon release of the pressure differential.

In the case of the baseball bat 11 illustrated, it may be desirable toleave the grip's boot 15 on the knob 16 of the bat after the grip hasbeen installed thereon. Alternatively, it may be desirable to remove thegrip's boot from the baseball bat so as to provide a bat moreaesthetically similar to bats presently known to the game of baseball.If removal of the grip's boot 15 is desired, a razor blade (not shown)need merely be used to circumferentially slit the boot from the tubularportion 14 of the grip along line 73 (see FIG. 9) after the grip hasbeen applied to the bat's handle as shown in FIGS. 5-8. The boot 15 isthereafter removed from the bat's knob 16 simply by peeling same off theknob. As mentioned, this slitting step is not required and, indeed, maybe undesirable if the user, at a subsequent date, wishes to remove thegrip from the baseball bat by the same vacuum method means (but inreverse sequence) by which it was applied. Of course, removal of thegrip 10 from the bat's handle 12 by the vacuum means cannot be achievedunless the grip is closed at one end by the boot 15 as, otherwise, nopressure differential relation by vacuum could be achieved between thegrip's interior 70 and exterior 71.

Note particularly that this installation method permits simple and easyinstallation of a grip on an implement's handle when that handle is of avariable or non-uniform girth and/or cross-sectional area from one endthereof to the other (e.g., a baseball bat handle), as well as on animplement handle that is of other than a cylindrical shape (e.g., ahexagonal tennis racket handle). Further, and as described, theinstallation method permits field installation as well as installationat the factory because of the relatively low vacuum requirementsnecessary to stretch or expand a grip 10 fabricated in accord with theprinciples of this invention. Additionally, the method is capable ofbeing executed very quickly.

I claim:
 1. A method of providing a grip on the handle of a hand-heldimplement, said implement having a free end type handle, and said gripbeing comprised of a tubular member open at one end and a boot integralwith said tubular member that closes its other end, said methodcomprisingdipping, into an elastomeric latex, a male mandrel having saidgrip's approximately as-produced and before-installation size, geometry,and exterior surface characteristics to form said grip, said grip beingprovided with an average internal girth between about 5 and about 50%less than the average external girth of said handle for that portion ofsaid handle on which said grip is to be mounted, an average wallthickness of between about 0.01 inches and about 0.10 inches, apercentage elongation at break between about 400 and about 1000%, atensile strength at break between about 2000 psi and about 6000 psi, anda modulus at 200% elongation between about 100 psi and about 500 psi,stripping the latex skin from said mandrel after said skin has cured,said skin being turned inside out as same is stripped, thereby orientingthe as-produced grip's exterior surface on the outside of said grip,exposing the exterior surface of said grip to a vacuum sufficient toexpand said grip throughout its longitudinal axis, said expansion beingsufficient to permit said implement's handle to be inserted thereinwithout touching the interior surface of said grip while the exteriorsurface is exposed to said vacuum, orienting the free end of saidimplement's handle adjacent the open end of said grip, inserting saidimplement's handle into said grip free end first until said free endbottoms out adjacent said grip's boot, bottoming out of said free endadjacent said boot serving to properly position said handle relative tosaid grip, and thereafter releasing said vacuum from the exterior ofsaid grip, same permitting said grip to contract into a friction fitrelation with said implement's handle.
 2. An installation method as setforth in claim 1 including the step ofsupporting said grip fromunderneath said grip's boot when said grip is vertically oriented duringinstallation.
 3. An installation method as set forth in claim 1 whereinsaid vacuum is created by one of hand and foot operated vacuum pumps. 4.An installation method as set forth in claim 1 includingcuffing the openend of said tubular member over a vacuum chamber's collar to aid indefining an airtight chamber within which said grip is positioned priorto exposing said grip to a vacuum.
 5. An installation method as setforth in claim 1 wherein said vacuum created is between about 12 inchesmercury and about 20 inches mercury.
 6. An installation method as setforth in claim 1 wherein said hand-held implement is one of a baseballbat, a tennis racquet and a golf club.
 7. An installation method as setforth in claim 1 wherein said elastomeric latex is a rubber latex.
 8. Aninstallation method as set forth in claim 1 including the stepsofpreheating said mandrel prior to dipping same in said elastomericlatex, and passing said mandrel through a curing oven after dipping samein said latex.